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sum-root-to-leaf-numbers.py
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sum-root-to-leaf-numbers.py
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# Time: O(n)
# Space: O(h), h is height of binary tree
#
# Given a binary tree containing digits from 0-9 only, each root-to-leaf path could represent a number.
#
# An example is the root-to-leaf path 1->2->3 which represents the number 123.
#
# Find the total sum of all root-to-leaf numbers.
#
# For example,
#
# 1
# / \
# 2 3
# The root-to-leaf path 1->2 represents the number 12.
# The root-to-leaf path 1->3 represents the number 13.
#
# Return the sum = 12 + 13 = 25.
#
# Definition for a binary tree node
class TreeNode:
def __init__(self, x):
self.val = x
self.left = None
self.right = None
class Solution:
# @param root, a tree node
# @return an integer
def sumNumbers(self, root):
return self.sumNumbersRecu(root, 0)
def sumNumbersRecu(self, root, num):
if root is None:
return 0
if root.left is None and root.right is None:
return num * 10 + root.val
return self.sumNumbersRecu(root.left, num * 10 + root.val) + self.sumNumbersRecu(root.right, num * 10 + root.val)
if __name__ == "__main__":
root = TreeNode(1)
root.left = TreeNode(2)
root.right = TreeNode(3)
print Solution().sumNumbers(root)